Lens barrel that changes focal length and image pickup apparatus equipped with lens barrel

ABSTRACT

A lens barrel that is capable of decreasing a barrel length under a retracted condition by simplifying a configuration. The lens barrel changes a focal length by moving first and second lens groups in an optical axis direction. A light-amount adjusting member is located between the first and second lens groups. First, second, third holding frames hold the first lens group, the second lens group, and the light-amount adjusting member, respectively. A cam mechanism moves the first, second, and third holding frames in the optical axis direction so that a part of the second lens group is inserted into the aperture of the light-amount adjusting member and concave and convex surfaces of the first and second lens groups are overlapped in the optical axis direction under a retracted condition. The aperture diameter of the light-amount adjusting member is enlarged when shifting to the retracted condition from a shooting condition.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 12/797,995,filed Jun. 10, 2010, the entire disclosure of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens barrel that changes a focallength, increases a barrel length under a shooting condition, anddecreases the barrel length under a retracted condition, and to an imagepickup apparatus equipped with the lens barrel.

2. Description of the Related Art

Conventionally, various techniques to shorten the barrel length underthe retracted condition have been suggested with respect to a zoom lensbarrel that increases the barrel length under the shooting condition anddecreases the barrel length under the retracted condition to retract thelens barrel into a camera body (a retractable lens).

Japanese Laid-Open Patent Publication (Kokai) No. 2004-347615(JP2004-347615A) discloses a lens barrel that can further decrease alength in an optical axis direction (the barrel length) as compared withan ordinary retractable lens barrel that can extend and can be retractedinto a camera body, and a camera equipped with such a lens barrel. FIG.17 is a sectional view showing a configuration of the conventional lensbarrel described in the above-mentioned publication. This lens barrel800 is capable of varying its barrel length between a retractedcondition with a short barrel length and a shooting condition with along barrel length. The lens barrel 800 reduces a length in an opticalaxis direction by opening an aperture of a lens shutter 900 andinserting a lens group 852 into the aperture under the retractedcondition.

Moreover, Japanese Laid-Open Patent Publication (Kokai) No. H10-111444(JP H10-111444A) discloses a zoom lens barrel with a shutter that isable to shorten a length in an optical axis direction under theretracted condition.

However, the above-mentioned conventional lens barrel has a problem thatthe barrel length under the retracted condition cannot be shortenedenough.

Moreover, the lens barrel in the Japanese Laid-Open Patent Publication(Kokai) No. 2004-347615 (JP 2004-347615A) has a configuration where alight-amount control member such as a lens shutter is openedcompulsorily more greatly than the maximum aperture at the time ofshooting by a rodlike member, when the lens barrel shifts to theretracted condition from the shooting condition. Accordingly,unnecessary power is applied to the light-amount control member, whichmay break the light-amount control member.

SUMMARY OF THE INVENTION

The present invention provides a lens barrel and an image pickupapparatus with the lens barrel that are capable of decreasing a barrellength under the retracted condition by simplifying a configuration.Moreover, the present invention provides a lens barrel and an imagepickup apparatus that are capable of preventing a breakage of thelight-amount adjusting member.

Accordingly, a first aspect of the present invention provides a lensbarrel that changes a focal length by moving at least one of a firstlens group and a second lens group in an optical axis direction, andthat increases a barrel length under a shooting condition and decreasesthe barrel length under a retracted condition, comprising a firstholding frame adapted to hold the first lens group, a second holdingframe adapted to hold the second lens group, a light-amount adjustingmember adapted to adjust an amount of light that transmits an opticalsystem by changing a diameter of an aperture, the light-amount adjustingmember being located between the first lens group and the second lensgroup, a third holding frame adapted to hold the light-amount adjustingmember, and a cam mechanism adapted to move the first, second, and thirdholding frames in the optical axis direction so that a part of thesecond lens group is inserted into the aperture of the light-amountadjusting member and concave and convex surfaces, which are faced toeach other, of the first and second lens groups are overlapped in theoptical axis direction under the retracted condition, wherein thediameter of the aperture of the light-amount adjusting member isenlarged and the first, second, and third holding frames are moved inthe optical axis direction, when shifting to the retracted conditionfrom the shooting condition.

Accordingly, a second aspect of the present invention provides an imagepickup apparatus comprising, a lens barrel adapted to change a focallength by moving at least one of a first lens group and a second lensgroup in an optical axis direction, to increase a barrel length under ashooting condition, and to decrease the barrel length under a retractedcondition, comprising a first holding frame adapted to hold the firstlens group, a second holding frame adapted to hold the second lensgroup, a light-amount adjusting member adapted to adjust an amount oflight that transmits an optical system by changing a diameter of anaperture, the light-amount adjusting member being located between thefirst lens group and the second lens group, a third holding frameadapted to hold the light-amount adjusting member, and a cam mechanismadapted to move the first, second, and third holding frames in theoptical axis direction so that a part of the second lens group isinserted into the aperture of the light-amount adjusting member andconcave and convex surfaces, which are faced to each other, of the firstand second lens groups are overlapped in the optical axis directionunder the retracted condition, a control unit adapted to control thelight-amount adjusting member so as to enlarge the diameter of theaperture and to control the cam mechanism so as to move the first,second, and third holding frames in the optical axis direction, whenshifting to the retracted condition from the shooting condition.

According to the present invention, when shifting to the retractedcondition from the shooting condition, the part of the second lens groupis inserted into the aperture of the light-amount adjusting member andthe concave and convex surfaces, which are faced to each other, of thefirst and second lens groups are overlapped in the optical axisdirection. Accordingly, the configuration is simplified and the barrellength under the retracted condition is shortened.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an external appearance of a digitalcamera that is provided with a lens barrel according to an embodiment ofthe present invention.

FIG. 2 is a block diagram schematically showing configurations of acontrol unit and peripheral circuits of the digital camera in FIG. 1.

FIG. 3 is a sectional view showing a configuration of the lens barrelaccording to the embodiment under a retracted condition.

FIG. 4 is a sectional view showing the configuration of the lens barrelaccording to the embodiment under a shooting condition.

FIG. 5 is an exploded perspective view showing a configuration of adiaphragm unit of the lens barrel according to the embodiment.

FIG. 6 is a view showing a configuration of the diaphragm unit of thelens barrel according to the embodiment viewed in an optical axisdirection.

FIG. 7 is a view showing the configuration of the diaphragm unit of thelens barrel according to the embodiment viewed in an optical axisdirection.

FIG. 8 is a view showing the configuration of the diaphragm unit of thelens barrel according to the embodiment viewed in an optical axisdirection.

FIG. 9 is a view showing configurations of a straight moving barrel, arotating barrel, the diaphragm unit, and a shutter unit of the lensbarrel according to the embodiment.

FIG. 10 is a development view showing cam grooves formed on the rotatingbarrel of the lens barrel according to the embodiment.

FIG. 11 is a view showing external appearances of the diaphragm unit andthe shutter unit of the lens barrel according to the embodiment underthe shooting condition viewed in an optical axis direction.

FIG. 12 is a sectional view showing structures of the diaphragm unit andthe shutter unit viewed in a direction of an arrow A-A line in FIG. 11.

FIG. 13 is a view showing the external appearances of the diaphragm unitand the shutter unit of the lens barrel according to the embodimentunder the retracted condition viewed in the optical axis direction.

FIG. 14 is a sectional view showing structures of the diaphragm unit andthe shutter unit viewed in a direction of an arrow B-B line in FIG. 13.

FIG. 15 is a flowchart showing operation procedures to shift the lensbarrel to the retracted condition from the shooting condition whenturning OFF a main power of the digital camera in FIG. 1.

FIG. 16 is a flowchart showing operation procedures to shift the lensbarrel to the retracted condition from the shooting condition when anerror occurs under the shooting condition of the digital camera in FIG.1.

FIG. 17 is a sectional view showing a configuration of a conventionallens barrel.

DESCRIPTION OF THE EMBODIMENTS

Hereafter, embodiments according to the present invention will bedescribed in detail with reference to the drawings.

A lens barrel of this embodiment is mounted on a digital camera as animage pickup apparatus. This lens barrel has a retractable zoommechanism (a collapsible-mount-type zoom mechanism) with a variablefocal length, increases a barrel length under a shooting condition, anddecreases the barrel length under a retracted condition to retract thelens barrel into a camera body.

FIG. 1 is a perspective view showing an external appearance of thedigital camera 12 that is provided with the lens barrel 71 according tothe embodiment. A finder 17 for determining composition of a subject, anauxiliary light source 16 for assisting photometric measurement anddistance measurement, an electric flash 18, and the lens barrel 71 aremounted on a front side of the digital camera 12. It should be notedthat FIG. 1 shows the condition where the main power of the digitalcamera 12 is OFF and the lens barrel (an image pickup lens barrel) 71 isunder the retracted condition.

A release button 13, a power supply change button 15, and a zoom switch14 are arranged on an upper surface of the digital camera 12. A tripodfitting part (not shown) and a card battery cover (not shown) arearranged on a bottom surface of the digital camera 12. A memory carddrive 42 and a battery insert portion (not shown) that will be describedlater are arranged inside the card battery cover.

Operation buttons 21, 22, 23, 24, 25, and 26 that are used to switchvarious functions; a display 20 (see FIG. 2) that consists of LCD; and afinder eyepiece (not shown) are arranged on a back surface of thedigital camera 12. An operation mode of the digital camera 12 isselected by depressing the manual operation buttons 21 through 26 fromamong a shooting mode, a reproduction mode, a moving image shootingmode, or the like. The display 20 displays image data stored in a memory40 or image data read from a memory card. When the reproduction mode isselected, the display 20 displays a plurality of shooting data with areduced size.

FIG. 2 is a block diagram schematically showing configurations of acontrol unit and peripheral circuits of the digital camera 12. A controlunit 50 mainly consists of a CPU 46, a ROM 45, and a RAM 47. The controlunit 50 and various components such as the release button 13, theoperation buttons 21 through 26, the display 20, the memory 40, and thememory card drive 42 are connected via a bus 44.

A zooming motor driving unit 29, a focusing motor driving unit 31, ashutter driving unit 32, a diaphragm driving unit 35, an image pickupdevice 105 such as a CCD and a CMOS, and the electric flash 18 areconnected to a driving circuit 43 that is connected with the controlunit 50 via the bus 44. The zoom motor driving unit 29 drives alens-barrel driving motor 29 a. The focusing motor driving unit 31drives a focusing motor 31 a. These units are controlled by signals fromthe control unit 50. Control programs to control the above-mentionedvarious constitution elements are stored in the ROM 45. Data requiredfor the respective control programs is stored in the RAM 47.

In the digital camera 12 having the above-mentioned configuration, whena user presses the power supply change button 15 to turn the power ONfrom OFF, the CPU 46 reads a necessary control program from the ROM 45,and starts an initial operation. That is, the control unit 50 shifts thelens barrel 71 to a predetermined shooting condition, and starts ashooting function so that the camera is made into a shooting standbystate.

When the user presses the release button 13 to take a picture, thecontrol unit 50 detects brightness (a photometry value) of a subject bythe image pickup device 105, sets an aperture value and a shutter speedbased on the photometry value, and determines whether the electric flash18 will be emitted or not. By operating the operation button 21beforehand, the user can also select a flash mode from among aforced-emission mode to force the electric flash 18 to emit and ano-emission mode to prohibit an emission.

Next, the control unit 50 measures a distance to the subject, andcontrols the focusing motor driving unit 31 so as to move a focusinglens member 30 to a predetermined in-focus position. Accordingly, animage pickup lens focuses on the subject. It should be noted that athird lens group 104 mentioned later is used for the focusing lensmember 30.

The control unit 50 controls the shutter driving unit 32 so as to openand close a shutter (the shutter unit) 201, and makes the image pickupdevice 105 capture a desired image. Electrical charge corresponding to alight amount that enters based on an exposure value is accumulated bythe image pickup device 105. The electrical charge is converted into animage signal, which is outputted to an analog signal processing unit 36.

The analog signal processing unit 36 applies an analog signal process tothe captured image signal, and outputs to an A/D conversion unit 38. TheA/D conversion unit 38 converts the received analog data into digitaldata. The digital data is outputted to a digital signal processing unit39, and the digital data is processed here. Finally, the digital data isstored into the memory 40.

A compression-extension unit 41 applies a compression process or thelike such as JPEG and TIFF to the digital data stored in the memory 40in response to an operation of the operation button 22. Then, theprocessed data is outputted to the memory card drive 42, and is storedinto the memory card. It should be noted that the digital data processedby the digital signal processing unit 39 is outputted to thecompression-extension unit 41 and is stored into the memory card by thememory card drive 42, when the digital camera 12 does not have a memory40.

The control unit 50 controls the compression-extension unit 41 to applyan expansion process to the image data stored in the memory 40 or theimage data stored in the memory card by the memory card drive 42, anddisplays the processed image data on the display 20 via the bus 44. Whenthe user who looks at the data indicated on the display 20 determinesthat the image is unnecessary, the user can delete data by operating theoperation button 23.

When the user operates the zoom switch 14 arranged on the upper surfaceof the digital camera 12, the zoom motor driving unit 29 is controlledby the control unit 50 through the driving circuit 43 so that the lensbarrel 71 extends/contracts in an optical axis direction of an opticalsystem (the direction of an optical axis passing through centers oflenses). The user can perform what is called digital zoom that enlargesor reduces a stored image displayed on the display 20 by operating thezoom switch 14.

Next, a configuration of the lens barrel 71 of the digital camera 12will be described. FIG. 3 is a sectional view showing the configurationof the lens barrel 71 under the retracted condition. FIG. 4 is asectional view showing the configuration of the lens barrel 71 under theshooting condition.

An optical system arranged in the lens barrel 71 is constituted byarranging a first lens group 102, a diaphragm unit 301, a second lensgroup 209, the shutter 201, the third lens group 104, a filter 106, andthe image pickup device 105 along the optical axis 101 in this orderfrom a subject side that is a left side in FIG. 3 and FIG. 4. It shouldbe noted that although each of the lens groups is shown as asingle-piece lens in the figures, it is constituted as a combination ofa plurality of lenses in fact.

The lens barrel 71 is provided with a fixing barrel 400 that surroundsthe outermost position, a rotating barrel 402 that is driven by the zoommotor 29 a to be rotated inside the fixing barrel 400, a cylinder 150that is inserted inside the rotating barrel 402 from the subject side,and a straight moving barrel 401 that is inserted inside the rotatingbarrel 402 from the side of the image pickup device 105. The rotatingbarrel 402 moves in the optical axis direction by rotating. Although thestraight moving barrel 401 moves in the optical axis direction with therotating barrel 402, it goes straight on without rotating.

The second lens group 209 is fixed to a shutter base 202 (a secondholding frame). The shutter 201 is mounted on the shutter base 202.Three advance guide parts 206 are formed on the shutter base 202radially at nearly regular intervals, and cam pins 207 are attached totip ends thereof. The cam pins 207 are engaged with cam grooves 403formed inside the rotating barrel 402. When the rotating barrel 402rotates, the shutter base 202 moves in the optical axis direction.

The diaphragm unit 301 is located between the first and second lensgroups 102 and 209 as a light-amount adjusting member that adjusts anamount of light that transmits the optical system by changing anaperture diameter, and is mounted on a diaphragm base 305 (a thirdholding frame). Three advance guide parts 314 are formed on thediaphragm base 305 radially at nearly regular intervals, and cam pins315 are attached to tip ends thereof. The cam pins 315 are engaged withcam grooves 404 formed inside the rotating barrel 402. When the rotatingbarrel 402 rotates, the diaphragm base 305 moves in the optical axisdirection.

The first lens group 102 is held by the cylinder 150 (a first holdingframe) that is movable in the optical axis direction with respect to therotating barrel 402. The cylinder 150 has follower parts that follow camgrooves (not shown) formed on the rotating barrel 402, and moves in theoptical axis direction according to a rotation of the rotating barrel402.

The third lens group 104 is held by a lens frame 108. The lens frame 108equips a screw guide 108 a at one edge thereof. The screw guide 108 a ismeshed with a worm gear 31 b fixed to a rotating shaft of the focusingmotor 31 a. When rotating the focusing motor 31 a, the third lens group104 moves in the optical axis direction.

Next, a configuration of the diaphragm unit 301 will be shown. FIG. 5 isan exploded perspective view showing the configuration of the diaphragmunit 301. FIG. 6, FIG. 7, and FIG. 8 are views showing the configurationof the diaphraym unit 301 viewed in the optical axis direction.

The diaphragm unit 301 comprises the diaphragm base 305, a diaphragmcover 306, a diaphragm ring 307, diaphragm blades 308, a diaphragmactuator 309, a gear 310, and a sensor 311.

A plurality of holes 313 into which rotating shafts 312 of the diaphragmblades 308 are inserted are formed on the diaphraym base 305 at nearlyregular intervals in the circumferential direction around the opticalaxis 101. The gear 310 is attached to the driving shaft of the diaphragmactuator 309. The diaphragm actuator 309 is fixed to the diaphragm base305.

A plurality of cam grooves 316 with which bosses 317 of the diaphragmblade 308 are engaged are formed on the diaphraym ring 307 at nearlyregular intervals in the circumferential direction around the opticalaxis 101. A gear part 318 that meshes with the gear 310 and a detectedpart 322 that is detected by the sensor 311 are formed on the diaphragmring 37. It should be noted that the combination of the sensor 311 andthe detected part 322 is an example of a position detecting unit.

The rotating shaft 312 and the boss 317 are formed on the diaphraymblade 308. The rotating shaft 312 is inserted into the hole 313 formedon the diaphragm base 305. The boss 317 is inserted into the cam groove316 formed on the diaphragm ring 307.

The plurality of diaphraym blades 308 are arranged at the nearly regularintervals around the optical axis 101. The plurality of diaphragm blades308 form an aperture 319 of which a size is variable in response to anoverlapping condition of the diaphragm blades 308.

When the diaphragm ring 307 is driven by the power of the diaphragmactuator 309, each of the diaphragm blades 308 moves so as to rotatealong the cam groove 316 of the diaphragm ring 307 around the rotatingshaft 312, and the aperture 319 of the diaphragm unit 301 will be set ata desired size.

Under the shooting condition, the diaphragm unit 301 of this embodimentadjusts the light amount by changing the size of the aperture 319 formedof diaphragm blade 308. On the other hand, under the retractedcondition, the plurality of diaphragm blades 308 are stored in positionsouter than the maximum aperture d and inner than the outer diameter ofthe diaphragm base 305 in order to prevent interference with the secondlens group 209. That is, the plurality of diaphragm blades 308 shift toa super-full aperture condition where the aperture is opened stilllarger than the maximum aperture under the shooting condition. Here, theinner side of the maximum aperture d under the super-full aperturecondition is defined as a super-full aperture 320.

The sensor 311 is fixed to the diaphragm base 305. The condition of thediaphragm blades 308 is grasped by detecting the position of thedetected part 322 formed on the diaphragm ring 307. In this embodiment,the sensor 311 is arranged so as to detect the detected part 322 whenthe diaphragm blades 308 are stored in the diaphragm base 305 and shiftto the super-full aperture condition where the aperture is opened stilllarger than the maximum aperture under the shooting condition.

FIG. 9 is a view showing configurations of the straight moving barrel401, the rotating barrel 402, the diaphragm unit 301, and the shutterunit 201. FIG. 10 is a development view showing the cam grooves 403 and404 formed on the rotating barrel 402.

Slits 405 are formed on the straight moving barrel 401 so that theadvance guide parts 206 provided on the shutter unit 201 (a light-amountvarying member) and the advance guide parts 314 provided on thediaphragm unit 301 are engaged. It should be noted that a rotation ofthe straight moving barrel 401 is prohibited by a straight movementcontrol member (not shown).

The rotating barrel 402 is rotatable and movable in the optical axisdirection with respect to the straight moving barrel 401. As mentionedabove, the cam grooves 403 with which the cam pins 207 provided at thetip end of the advance guide parts 206 are engaged, and the cam grooves404 with which the cam pins 315 provided at the tip ends of the advanceguide parts 314 are engaged are formed on the inner surface of therotating barrel 402.

The advance guide parts 314 and 206 are inserted into the slits 405 ofthe straight moving barrel 401, and the cam pins 207 and 315 provided atthe respective tip ends are located in the cam grooves 403 and 404formed on the rotating barrel 402. Accordingly, the straight movingbarrel 401 and the rotating barrel 402 hold the diaphragm unit 301 andthe shutter unit 201.

Here, when rotating the rotating barrel 402 relatively to the straightmoving barrel 401, the shutter unit 201 and the diaphragm unit 301 movein the direction of the optical axis 101. A distance between the shutterunit 201 and the diaphragm unit 301 is maintained at a fixed interval406 under the shooting condition by means of the cam grooves 403 and 404formed on the rotating barrel 402. However, since the interval betweenthe cam groove 403 and the cam groove 404 decreases to an interval 407when shifting to the retracted condition from the shooting condition,the shutter unit 201 and the diaphragm unit 301 become close to eachother. Accordingly, the barrel length under the retracted condition canbe reduced.

It should be noted that although the shutter unit 201 and the diaphragmunit 301 are moved while keeping the distance therebetween under theshooting condition in this embodiment, they can be moved while changingthe distance, which increases a degree of freedom of the optical system.Since the shutter unit 201 and the diaphragm unit 301 are held anddriven by the straight moving barrel 401 and the rotating barrel 402,the structure of the lens barrel is simplified.

Next, the diaphragm unit 301 and the shutter unit 201 under the shootingcondition and the retracted condition will be described. FIG. 11 is aview showing external appearances of the diaphragm unit 301 and theshutter unit 201 under the shooting condition viewed in the optical axisdirection. FIG. 12 is a sectional view showing structures of thediaphragm unit 301 and the shutter unit 201 viewed in a direction of anarrow A-A line in FIG. 11.

FIG. 13 is a view showing the external appearances of the diaphragm unit301 and the shutter unit 201 under the retracted condition viewed in theoptical axis direction. FIG. 14 is a sectional view showing structuresof the diaphragm unit and the shutter unit viewed in a direction of anarrow B-B line in FIG. 13.

The shutter unit 201 and the diaphragm unit 301 are arrangedindependently so as to sandwich the second lens group 209 in thedirection of the optical axis 101. The shutter unit 201 is arrangedcloser to the image pickup device 105 than the diaphragm unit 301.

The shutter unit 201 comprises a part of the shutter base 202, a shutterblade 203, a shutter cover 204 (see FIG. 12), and a shutter actuator(not shown). The shutter blade 203 consists of one or plural bladesdependent on its space. The shutter blade 203 can be opened and closedusing a power of the shutter actuator, and is held under a fully-openedcondition or a totally closed condition in a no-electricity status.

FIG. 15 is a flowchart showing operation procedures to shift the lensbarrel 71 to the retracted condition from the shooting condition whenturning OFF the main power. This processing program is stored in the ROM45 in the control unit 50, and is executed by the CPU 46 when the mainpower is turned OFF.

When the lens barrel 71 shifts to the retracted condition from theshooting condition, first, the control unit 50 determines whether thesensor 311 detects the position of the detected part 322 mounted on thediaphraym ring 307 (step S1). When the position of the detected part 322is not detected, the control unit 50 checks the condition of theaperture 319 of the diaphragm blades 308, and drives the diaphragmactuator 309 according to the condition (step S2). And the control unit50 returns the process to the step S1.

On the other hand, when the control unit 50 confirms that the diaphragmunit 301 is under the super-full aperture condition based on a signalfrom the sensor 311, the control unit 50 shifts the lens barrel 71 tothe retracted condition from the shooting condition (step S3), andfinishes this process.

At this time, the diaphragm blades 308 are stored in positions outerthan the super-full aperture 320 of the diaphragm unit 301, and shift tothe super-full aperture condition where the aperture opens still largerthan the maximum aperture under the shooting condition, and are held inorder to prevent interference with the second lens group 209.

At least a part of the second lens group 209 enters into the super-fullaperture 320 of the diaphragm unit 301, and at least a part of thesecond lens group 209 overlaps with at least a part of the first lensgroup 102 in the optical axis direction. That is, a convex surface 321of the second lens group 209 enters into a recess portion of a concavesurface 107 of the first lens group 102. Accordingly, the total lengthof the lens barrel can be reduced (see FIG. 3).

FIG. 16 is a flowchart showing operation procedures to shift the lensbarrel 71 to the retracted condition from the shooting condition when anerror occurs under the shooting condition. This processing program isstored in the ROM 45 in the control unit 50, and is executed by the CPU46 in a predetermined cycle.

The control unit 50 determines whether an error such as an abnormalityof the digital camera 12 and a malfunction of the lens barrel 71 isoccurred under the shooting condition (step S11).

When an abnormality occurs in the digital camera 12 or when the lensbarrel 71 causes a malfunction under the shooting condition, the controlunit 50 checks the condition of the diaphragm unit 301 based on a signalfrom the sensor 311 (step S12). That is, the control unit 50 determineswhether the sensor 311 detects the position of the detected part 322mounted on the diaphragm ring 307.

When the control unit 50 determines that the diaphragm blades 308 arenot under the super-full aperture condition as a result of checking theaperture 319 of the diaphragm blades 308, the control unit 50 drives thediaphragm actuator 309 (step S13). And the control unit 50 returns theprocess to the step S1. On the other hand, when the control unit 50confirms that the diaphragm unit 301 is under the desired super-fullaperture condition based on the signal from the sensor 311, the controlunit 50 shifts the lens barrel 71 to the retracted condition from theshooting condition (step S14), and finishes this process.

Thus, the control unit 50 shifts the diaphragm blade 308 to thesuper-full aperture condition by checking the condition of the diaphragmunit 301 based on the signal from the sensor 311. Accordingly, a damageof the lens barrel 71 due to interference between the diaphragm blades308 and the second lens group 209, which occurs when the lens barrel 71is retracted while keeping the diaphragm blades 308 under the shootingcondition, is prevented.

Here, even when the lens barrel 71 is under the retracted condition, theshutter blade 203 can open and close regardless of the condition.Therefore, performance degradation of the image pickup device 105 andthe filter 106 attached to the image pickup device 105 can be preventedby closing the shutter blade 203 under the retracted condition.

In this embodiment, the lens surface 107 of the first lens group 102nearest to the second lens group 209 has a concave form, and the lenssurface 321 of the second lens group 209 nearest to the first lens group102 has a convex form. Under the retracted condition, these lenssurfaces are overlapped in the direction of the optical axis 101.Accordingly, the barrel length under the retracted condition can bereduced. It should be noted that the combination of the surface forms isarbitrary and is not limited in particular.

Since the distance between the shutter unit 201 and the diaphragm unit301 is not reduced when shifting to the retracted condition from theshooting condition or when receiving an external force such as a shockunder the shooting condition, damage to the shutter unit 201 and thediaphragm unit 301 can be prevented.

In the lens barrel of this embodiment, when shifting to the retractedcondition from the shooting condition, the second lens group 209 entersinto the super-full aperture 320 of the diaphragm unit 301, and thesecond lens group 209 and the first lens group 102 are held so that theyare overlapped in the optical axis direction. Accordingly, theconfiguration is simplified and the barrel length under the retractedcondition can be reduced.

Under the super-full aperture condition, since the second lens group 209is held while being entered into the super-full aperture 320 of thediaphragm unit 301, damage to the diaphragm unit 301 can be prevented.

Since the lens barrel shifts to the retracted condition after checkingthat the diaphragm blades 308 are in the super-full aperture condition,contact between the lens and the blades can be prevented.

Since the shutter unit 201 is totally closed under the retractedcondition, degradation of the image pickup device 105 can be prevented.

Since the shutter unit 201 does not approach the diaphragm unit 301 whenreceiving an external force such as a shock under the shootingcondition, damage to the diaphragm unit 301 due to contact between thelens and the blades can be prevented.

Since the shutter unit 201 is arranged at the opposite side of thediaphragm unit 301 across the second lens group 209, the shutter unit201 can be arranged near the image pickup device 105.

It should be noted that the present invention is applicable to not onlythe configuration of the above-mentioned embodiment, but also anyconfigurations as long as the functions shown in the claims or thefunctions of the configuration of the embodiment can be achieved.

Although the diaphragm unit 301 becomes the super-full aperturecondition and the shutter unit 201 becomes the totally closed conditionin this embodiment, such conditions are not limited in particular. Forexample, a configuration where the shutter unit 201 fully opens as thelight-amount adjusting member and the diaphragm unit 301 totally closesas the light-amount varying member, and a configuration where thelight-amount adjusting member such as an ND filter is used instead ofthe diaphragm unit 301 may be adopted.

The configurations or allocations of the guide part, the pressurizationpart, etc. are not limited to those of the above-mentioned embodiment,and can be changed suitably.

Although the lens barrel of this embodiment is constituted as asingle-piece design with the image pickup apparatus, it may beexchangeably equipped with the image pickup apparatus.

In the above-mentioned embodiment, although the digital camera has beendescribed as an example of the image pickup apparatus, the presentinvention is also applicable to a digital video camera etc.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2009-147579, filed on Jun. 22, 2009, which is hereby incorporated byreference herein in its entirety.

1. A lens barrel that changes a focal length by moving at least one of afirst lens group and a second lens group in an optical axis direction,and that increases a barrel length under a shooting condition anddecreases the barrel length under a retracted condition, comprising: afirst holding frame adapted to hold the first lens group; a secondholding frame adapted to hold the second lens group; a light-amountadjusting member adapted to adjust an amount of light that transmits anoptical system by changing a diameter of an aperture, said light-amountadjusting member being located between said first lens group and saidsecond lens group; a third holding frame adapted to hold saidlight-amount adjusting member; and a cam mechanism adapted to move saidfirst, second, and third holding frames in the optical axis direction sothat a part of the second lens group is inserted into the aperture ofsaid light-amount adjusting member and concave and convex surfaces,which are faced to each other, of the first and second lens groups areoverlapped in the optical axis direction under the retracted condition,wherein the diameter of the aperture of said light-amount adjustingmember is enlarged and said first, second, and third holding frames aremoved in the optical axis direction, when shifting to the retractedcondition from the shooting condition.